The present invention relates to a portable apparatus for generating electrical power, a system for generating and harvesting your own electrical power, and a method for generating and harvesting your own electrical power. The preferred embodiment also extends to a printed coil laminate and an apparatus for generating electrical power including a printed coil laminate. The preferred embodiment relates generally to harvesting energy from movement of a user—a by-product of either human exercise (active movement) or, for example, public transportation (passive movement). Active movement could be walking, running, aerobics, etc. Passive movement could be sitting on a train, or travelling in a car or on motorcycle. It is desired to store that energy so that it can then be either utilised either directly by a portable electronic device or, alternatively, the energy may be fed back into the mains supply grid and the cost of the energy credited back to the user, for example, by means of Government sponsored feed in tariffs.
Harvesting energy from human powered motion during exercise is known. Known arrangements typically involve the incorporation of a component, such as a conventional style AC generator, which is then coupled to a part of a piece of exercise equipment, such as a flywheel of an exercise bicycle, by means of an axle to axle drive belt, or a sprung friction wheel. Alternatively, other arrangements have utilised an existing electromagnetic load found within some equipment, and harvest that energy rather than dissipate it through a resistive load providing a heat-sink to the environment.
Harvesting energy from vibration is also known. Arrangements in this field have used technology such as piezoelectric elements, whose length and thickness are selected in order to resonate at the dominant resonant frequency of the system. Issues and problems associated with these existing devices centre around the fact that they are only suitable for generating energy from relatively high frequency vibration of, say, greater than 50 Hz and the amount of energy generated is quite small and, so, these types of devices tend to only find applications for local (off grid) power generation—for example, in remote sensors that are located in an environment experiencing high frequency vibration.
Harvesting energy from random kinetic energy movement is known and can be exemplified by a kinetic winder/charger in a watch. However, in comparison to other portable electronic devices, watches are much smaller and have a lower power consumption. Therefore, whilst this technology might suit watches, it is not suitable for powering larger drain electronic devices.
Harvesting energy from parasitic energy for example energy from compressive or impact forces (such as road or foot traffic) is known. Typically, only a small amount of energy may be harvested from a device of this kind in relation to the relatively costly infrastructure for capturing, storing and/or offloading that energy. Further, the device may further act as a damping force, thereby reducing energy efficiency.
A major disadvantage of known systems is their cost. The cost of components is relatively high in comparison to the value of the energy which can be harvested. For example, during cardiovascular exercise, the average user can maintain a continuous workload which equates to approximately up to 200 W of expended energy—this is considered an approximate maximum load beyond which the average person would not be able to pedal. Owing to losses within any system, the expended energy is, therefore, nearer to 150 W. Although prices fluctuate and, in general rise with time, an exemplary commercial electricity unit cost of £0.08 per kWh equates to a value of £ 0.008 per hour of cardiovascular energy. Obviously then, it is likely to take some time to pay back capital expenditure on equipment before starting to save money.
Furthermore, neodymium (NdFeB) magnets are expensive and are considered a critical resource. At present, the relative cost of NdFeB magnets is roughly double that of ferrite magnet relative to their BH/max value (which is a measure of the stored energy in the magnet). Whilst ferrite technology is older and less efficient, there are sometimes important reasons (cost being an example) why one might wish to use an inferior material.
It is therefore desired to provide a cost-effective consumer product which would more quickly allow the user to offset the cost of electricity supply by recovering energy associated with their various forms of active or passive movement.